In particular, the present invention relates to a numerical-control apparatus for cutting stone, stone-like material, glass, ceramic or metal.
According to the art, interpolated-axis cutting machines for performing cutting, along straight or curved paths, of slabs of natural stone, natural-stone conglomerates or ceramic material into sub-elements are known.
The machines in question usually comprise a gantry-like structure where the upper beam is adapted to move above a working table on which the slab being machined is positioned. The beam has, arranged thereon, a support carriage which is slidable along the beam and on which a working unit movable vertically, towards or away from the working table, is mounted.
Depending on the type of machining operation, the working unit may be equipped with a spindle comprising a cutting disk, a nozzle for performing cutting by means of a water jet, or a combination of these two technologies.
As is known, with the cutting disk it is possible to perform straight cuts in several directions, since the spindle with cutting disk is generally mounted on a support which is able to rotate about a vertical axis, i.e. perpendicular to the working table, making it possible to obtain straight-side polygonal elements.
With this type of technology it is possible to obtain a very high cutting speed together with structural simplicity and mechanical strength. Moreover it is possible to perform inclined cuts, between a position which is perpendicular and a position which is parallel to the working table. In fact, the support on which the spindle with cutting disk is mounted allows the latter to rotate about an axis parallel to the working surface.
However, it is not possible to perform cuts along curved paths and it is in any case difficult to produce geometric forms, even if a simple nature, without the disk damaging the surface adjacent to the edge of the shape which is to be obtained from the slab.
With water-jet cutting technology a jet of water at a high pressure (for example 3000-4000 bar), preferably containing suspended granules of abrasive material, such as sand, is directed against the slab to be cut. The path of the jet is controlled by a nozzle which is adjustable, also in directions inclined with respect to the working table generally between a direction perpendicular and a direction parallel thereto.
Since it is necessary to dampen the water jet and recover the water used and the particles of abrasive material, the working table on which the slab to be cut is positioned is provided with a metallic grid which covers a tank filled with water.
The main advantage of this technology consists in allowing the formation of cuts which are very precise, including curved cuts. This advantage, however, is accompanied by a high operating cost.
In the prior art constructional solutions where these two technologies are combined, such that the straight cuts are performed with the cutting disk and the precise or curved cuts are performed by the water jet, are known.
An example of this type of combined apparatus may be found in U.S. Pat. Nos. 7,748,373 and 8,365,715 which describe an apparatus with a gantry-like structure of the type described further above, in which the working unit is equipped with a spindle comprising a cutting disk and a water-jet cutting nozzle.
The structure of the machine is similar to that described above and envisages a beam movable above a working table along two tracks. The beam has, arranged thereon, a support carriage which is slidable along the beam and on which the working unit is mounted. The working unit is movable vertically, towards or away from the working table and is provided with a spindle rotating about a vertical axis and equipped with water jet cutting means and disk cutting means.
The water-jet cutting nozzle is movable vertically with respect to the disk-carrying spindle between two positions: a retracted or rest position, when the cutting disk is used, and an extracted or operating position, when the water jet is used.
The working table consists of a tank, similar to that described above, closed by an interchangeable metallic grid. A sacrificial element for preventing contact between cutting disk and grid is placed on top of the grid. The sacrificial element may consist, for example, of a wooden board and more conveniently elements made of plastic or rubber material which are inserted on top of the profiles which form the grid.
The apparatus described above, although it has several advantages compared to the preceding apparatus, is not without drawbacks.
In fact, in the combined apparatus of the known type, only the cutting disk can be inclined with respect to the working table, while the nozzle has a fixed orientation with the direction of the jet perpendicular to the working table.
However, in some applications it may be required to perform inclined cuts also using a water jet, for example in the case where undercuts must be performed along short straight or curved sections.
Carrying out these machining operations on a dedicated machine performing cutting only using a water jet would mean that any of advantages associated with the use of a combined apparatus would be lost, in particular as regards the possibility of being able to use, on a single apparatus, the most appropriate technology for each machining operation.
The object of the present invention is therefore to overcome the drawbacks of the prior art.